Sunday, July 25, 2010

Compass Siting

While we were at Lake Ontario, Dan had a plan to take the kids out to site with their compasses. It was really super hot this week and being out on the breakwater pier in the bright morning or mid-day sun didn't sound like a good idea. Finally, the opportunity presented itself and they started out with walkie talkies. I hung at base camp (the playground) and kept in communication. Had to call the team back in from the outpost due to an impending storm. I heard the life guards clear the beach and said, "Away team time to bring it in! Beach is closed due to that thunder you hear..." The away team rogered that and headed back in.

The second attempt was made from a different point right on the beach and it worked out well!

First the kids chose the first two sitings they wanted to make. Then they took the first siting by holding up a compass and holding its arrow toward the siting they wanted to make. They twisted the top until the North marking was in the same direction as North on the compass.

After that they took their bearing- that's the direction the point is from where you are. Next was the back bearing which means the opposite direction as your bearing. They marked where the point was on their map and then turned the compass so that the back bearing was pointing the same direction as the arrow on the compass. Dan had marked the maps with the difference between north and magnetic north lines. So, the kids lined up the lines on the compass with the lines on the map and drew the line using the side of the compass. They knew they were somewhere along that line.

Then they took a second bearing using the other object they had chosen, took the back bearing and drew another line. Where they intersect is supposed to be where you are standing. But they decided to take a third bearing just to be sure and if the third line intersected then that would have been their position.

a close up of the final result

Turns out the third bearing revealed a problem with the second bearing- a set of bluffs along the shore. So, they figured out where they were and realized their position was where the first and third bearing intersected were accurate, but the bluffs/cliffs were not a good bearing.

I8 could hardly wait to try this!

The kids had a google satellite image of the shore area and drew in their lines. They all came pretty close to their exact location.

The kids had a GREAT time doing this...only a homeschool family would do this on vacation. Yes? There are more compass sitings planned for our next trip in a few weeks and this time the kids will do magnetic declination!

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